1. Field of the Invention
The present invention relates to a housing and support structure for fuse-holding modules of the type intended for installation on vehicles, to receive in respective seats, formed in the modules, fuses, relays and similar electrical or electronic devices, as well as the necessary electrical connection terminations.
2. Description of the Related Art
To be able to satisfy different requirements with the same type of base components, groupable from time to time in different numbers or types, it has been known for some time to form these fuse-holding boxes as a structure in which many different rectangular parallelepiped-shaped fuse-holding modules are housed in a single container, or else, as described in EP-A-0508059 to compose the structure with a plurality of modules, each of which intrinsically forms a box, with a lid and a removable base, and is equipped, at its periphery, with fitting means and countermeans for removably attaching together the different modules and to thus form a unitary structure.
The same fitting means are used for the insertion of support rods or feet, through which the structure can be fixed through screws in the engine bay or on the shut-off partition between engine bay and passenger compartment. In the case of many fuse-holding modules housed in a single container, it has been proposed, like for example in EP-A-170455 to supply the different modules with fitting means for mutually attaching the different modules to each other, and then for attaching the set of modules inside a box.
For this purpose one or more modules can be supplied with screws for the fastening of the whole thing to the container.
In EP-A-170455 each module is equipped, on at least one side face, with overhanging tenons forming an interposed mortise having an undercut and with conjugated means (rod/groove) for the precise positioning of the two juxtaposed modules.
The conjugated means fit together two juxtaposed modules preventing any relative displacement of the modules in the juxtaposition plane and leaving only one degree of freedom: indeed, the modules are free to move away from each other.
A restriction which limits this degree of freedom is obtained with the use of a separate element of the tenon or double wedge type which simultaneously fits into the mutually interfacing mortises of the two juxtaposed modules and locks in position by effect of snap devices.
The construction of the structure is all the more laborious and requires different components.
From the constructive point of view the complexity of the profiles used to realize the coupling, besides involving a reduction in the useful volume of the module for housing the electrical components, involves a substantial fixed cost for the construction of the moulds necessary for production.
For the fixing of the whole of the modules to a support the use of auxiliary modules are foreseen fixed to the others with the same mutual attachment system and having through seats for fixing screws.
In fact manufacturing and assembling allowances may cause dimensional errors which do not allow for the use of the same mutual attachment system for a multiple and reliable fixing to a support or inside a container.
A similar approach, even if relatively simpler, is described in U.S. Pat. No. 4,469,393, which generally refers to modular connectors.
In U.S. Pat. No. 4,469,393 each module is equipped, on at least two side faces, with mating means (tenons on one face and mortise on the other) so that two modules can be fixed together inserting the tenon of one module into the mortise of the juxtaposed module.
Snap devices prevent the slipping of the tenon from the mortise.
The use of the coupling double wedge is thus eliminated, but not of the other elements, and for the fixing of the group of modules at least one dedicated module, equipped with a through-seat for fixing screws is necessary anyhow. In both cases the replacement of one module to remedy a possible malfunction or defect, or even only for reasons of updating and adaptation of the harness to new requirements, involves a laborious disassembly and decoupling operation of the different modules, besides the removal of the entire group of modules from the housing box or from the support.
The same drawback is present when the housing box is of a size and designed for allowing the addition of further optional modules, required only with the subsequent installation of accessories.
Also in this case it is necessary to remove the entire group of modules from the housing box, to couple the additional module with the pre-existing ones, possibly with a reconfiguration of them, and finally to put the whole thing back together again.
The present invention eliminates these drawbacks and provides a modular structure, consisting of a generically rectangular unitary frame, in which a plurality of parallelepiped rectangle-shaped fuse-holding modules, which are identical in size, with different functions according to requirements, are housed in the frame and directly removably fixed to it, without any mutual constraint, through a pair of opposite snap devices which engage two opposite faces of the module with two opposite walls of the frame.
In this way, still safeguarding the versatility of the structure, which can be adapted to the most diverse requirements, the construction and replacement operations of modules are made simpler and more reliable.
Also the structure of the individual modules is simplified, not being foreseen mutual coupling means which take up a certain amount of space, which cannot be used for the end use of the module, and a greater complexity of the production moulds, therefore a greater cost.
The frame is then equipped with a suitable number of feet or stirrups for fixing to the vehicle and lends itself in an extremely simple manner to the coupling with a protection cover and a base shell, together with which it goes to form a housing box for many fuse-holding modules.
Indeed, it is clear that to allow the insertion and the replacement of different electrical components in the modules, housed in the frame, said frame must be opened above and equipped with a removable cover for protecting the components from dust and possible sprays.
At the same time, to allow the insertion in the frame of different modules which, to avoid construction errors, generally come already wired, the base of the frame must be open, or else removably closed by a base shell equipped with suitable outlets for the passage of the electrical cables.
The frame, necessarily realised, like the cover and the base plate, in insulating material, preferably in thermoplastic material formed by injection moulding to combine the requirement of cost-effectiveness and ease of production with a good ability to elastically absorb knocks and stresses, cannot have a sufficient rigidity to guarantee the snap fixing of the modules onto its walls, even if the modules are fitted inside the frame.
The walls of the frame can deform elastically and, with respect to the desired configuration, can also be naturally deformed by effect of internal stresses which develop in the removal step from the mould and which are due to the shrinkage of the material as a consequence of local temperature differences. According to a further aspect of the present invention, this drawback, or rather the relative elasticity and deformability of the frame, is advantageously exploited and converted into an advantage which allows the clearances and productive allowances to be recovered, foreseeing, on the two opposite faces of the modules which have to be snap coupled with the walls of the frame, tenons which engage in corresponding seats of the walls of the frame, near to the snap fastening devices, and are capable of holding the walls of the frame in contact with the opposing faces of the modules, counteracting the stresses caused by the snap devices, and from possible internal stresses of the material which tend to move them apart.